A taxonomic key is used to identify a specific object. It is one of the most useful tools available to scientists trying to identify an unknown organism. For the given example, the characters for identification would be,
1. Presence of hairs on the skin: Cat, dog, cow, buffalo, goat, and sheep have hairs on the skin. Parrot, hen, and duck do not have hairs on the skin.
2. Presence of feathers: Cat, dog, cow, buffalo, goat, and sheep do not have feathers. Parrot, hen, and duck have feathers.
3. Modification of forelimbs into wings: In cat, dog, cow, buffalo, goat, and sheep, forelimbs are not modified. In parrot, hen, and duck, forelimb is modified into wings.
So, from this information, animals are classified into two categories, mammals and birds. Mammals include cat, dog, cow, buffalo, goat and sheep. Birds include parrot, hen and duck.